package main

import "fmt"
import "crypto/hmac"
import "crypto/sha256"
import "encoding/hex"

func main() {
	s := "hello world"
	mac := hmac.New(sha256.New, []byte(""))
	mac.Write([]byte(s))
	s = hex.EncodeToString(mac.Sum(nil))
	fmt.Printf("%s\n", s)
}
